Question

How do you solve `9x² + 42x = -49`?

Answer 1

`x = -7/3`

Explanation:

`9x^2 + 42x = -49`

Move all terms to LHS

`9x^2 + 42x + 49 = 0`

Now we factor

`(3x+7)(3x+7) = 0`

`(3x+7)^2 = 0`

Now we solve for `x`

`3x+7 = 0`

`3x = -7`

`x = -7/3`

Although this is a polynomial of degree `2` and you would expect `2` solutions, it turns out that there is one redundant solution, namely `x = -7/3`.